JP2006052845A - Porous friction material having nano particle as friction adjusting material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a novel friction material having high friction coefficient characteristics, judder resistance, and thermal resistance for a continuous torque transmission system having a continuous slip torque converter and a shifting clutch system. <P>SOLUTION: This friction material comprises a porous base material, at least one type of resin material, and at least one type of friction adjusting particles of nano particle size. The resin material is substantially uniformly distributed over the entire part of the base material. The discontinuous layer of the predetermined amount of the friction adjusting material of the nano particle size forms a porous upper surface on the surface of the base material. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a porous friction material having a first layer or lower layer comprising a porous substrate and a second layer or upper layer comprising at least one type of friction modifying particles comprising nanoparticles of friction modifying material. . The friction material of the present invention has a high coefficient of friction property, a very robust anti-shudder property and a very high heat resistance. The friction material also has improved strength, wear resistance and noise resistance.

  New and advanced continuous torque transmission systems with continuous slip torque converters and shifting clutch systems are being developed by the automotive industry. These new systems often have high energy requirements. Therefore, the friction material technology must also be developed to meet the increasing energy requirements of these advanced systems.

  In particular, there is a need for new, high performance and durable friction materials. The new friction material must be able to withstand high speeds such that the surface speed is up to about 65 m / sec. The friction material must also be able to withstand high facing lining pressures up to about 1500 psi. It is also important that the friction material be useful under limited lubricating conditions.

  To be useful in advanced systems, friction materials must be durable and have high heat resistance. The friction material must not only remain stable at high temperatures, but also must be able to quickly dissipate the high heat generated under the conditions of use.

  The fact that high speeds occur during engagement and disengagement of the new system means that the friction material must be able to maintain a relatively constant friction throughout the engagement. The frictional engagement is relatively constant over a wide range of speeds and temperatures, so that the transmission system during the “shuddering” of the material during braking or the power shift from one gear to another It is important to minimize “shuddering”. It is also important that the friction material has a desired torque curve shape so that there is no noise or “high noise” in the friction material during friction engagement.

  In particular, transmission systems and torque-on-demand systems incorporate slipping clutches primarily for fuel efficiency and driving comfort. The role of the slip clutch inside such a system changes from a wet start clutch of a vehicle starting device to a torque converter clutch. Depending on the operating conditions, slip clutches can be divided into three main classes: (1) low pressure and high slip speed clutches such as wet start clutches; (2) high pressure and low slip speed clutches such as Converter clutches; and (3) extremely low pressure and low slip speed clutches such as neutral to idle clutches.

  The primary performance concerns associated with all slip clutch applications are shudder prevention and friction interface energy management. Shuddering is caused by the friction characteristics of the friction material, the hardness and roughness of the mating surface, oil film retention, lubricant chemistry and interaction, clutch operating conditions, power transmission assembly and hardware. It can be due to a number of factors including wear alignment and power transmission contamination. Energy management at the friction interface is primarily related to interface temperature control and is affected by pump capacity, oil flow path and control method. The design of the friction material surface also contributes to the efficiency of interfacial energy management.

  Previously, asbestos fibers were included in the friction material for temperature stability. Asbestos is no longer used due to health and environmental issues. In more recent friction materials, attempts have been made to overcome the absence of asbestos in the friction material by modifying the impregnating paper or fiber material with phenolic resins or phenol-modified resins. However, these friction materials do not dissipate the high heat that is generated quickly, and the required heat resistance and satisfactory high coefficient of friction performance currently required for use in high speed systems currently under development. Does not have.

  Kearsey US Pat. No. 5,585,166 describes a multilayer friction lining having a porous substrate layer (cellulose and synthetic fibers, fillers and thermosetting resins) and a porous friction layer (nonwoven synthetic fibers in a thermosetting resin). Here, the friction layer has a higher porosity than the base layer.

  Seitz U.S. Pat. No. 5,083,650 includes a multi-step impregnation and curing method; that is, impregnating paper with a coating composition, placing carbon particles on the paper surface, and partially coating the coating composition in the paper. After curing, the second coating composition is applied to the partially cured paper and finally both coating compositions are cured.

  A variety of paper-based fibrous materials have been developed for use in friction materials, which are assigned to Borg Warner Inc., the assignee of the present invention. (BorgWarner Inc.). This reference is hereby incorporated by reference in its entirety.

  In particular, US Pat. No. 5,998,307 to Lam et al. Relates to a friction material having a primary fibrous base material impregnated with a curable resin, wherein the porous primary layer comprises at least one fibrous material. And the secondary layer includes carbon particles that cover at least about 3 to about 90% of the surface of the primary layer.

  Lam et al., U.S. Pat.No. 5,858,883, discloses a primary layer of less fibrillated aramid fibers, artificial graphite, and at least one type of filler, and a secondary layer comprising carbon particles on the surface of the primary layer; The present invention relates to a substrate having

  Lam et al. US Pat. No. 5,856,224 relates to a friction material comprising a substrate impregnated with a curable resin. The primary layer includes less fibrillated aramid fibers, artificial graphite, and fillers; the secondary layer includes carbon particles and a yield enhancer.

  Lam et al. U.S. Pat. No. 5,958,507 relates to a method of manufacturing a friction material, wherein carbon particles are present on about 3 to about 90% of at least one surface of a fibrous material comprising less fibrillated aramid fibers. Coating.

  Lam US Pat. No. 6,001,750 relates to a friction material comprising a fibrous base material impregnated with a curable resin. The porous primary layer comprises less fibrillated aramid fibers, carbon particles, carbon fibers, filler material, phenol novoloid fibers, and optionally cotton fibers. The secondary layer includes carbon particles that cover about 3 to about 90% of the surface.

  Yet another shared patent application No. 09 / 707,274 is a paper-type friction having a porous primary fibrous base material layer with friction modifying particles covering from about 3 to about 90% of the surface area of the primary layer. Regarding materials.

  In addition, various paper-type fibrous substrates are available from the shared BorgWarner Inc. Lam et al., U.S. Pat.Nos. 5,753,356 and 5,707,905, which describe a substrate containing less fibrillated aramid fibers, artificial graphite and fillers, such as References are also hereby fully incorporated by reference herein.

  Another shared Lam US Pat. No. 6,130,176 relates to a non-metallic and paper-type fibrous base material comprising less fibrillated aramid fibers, carbon fibers, carbon particles and fillers.

  For all types of friction materials, in order to be useful in “wet” applications, the friction material must have a wide variety of acceptable properties. The friction material must have good anti-shudder properties; have high heat resistance and be able to dissipate heat quickly; have long lasting, stable, and consistent friction performance. Must. If any of these properties are not met, optimal performance of the friction material is not achieved.

  It is also important to use a suitable impregnating resin in the friction material to form a friction material for high energy applications. The friction material must have good shear strength during use when brake fluid or transmission oil penetrates the friction material during use.

Accordingly, it is an object of the present invention to provide an improved friction material that is reliable and has improved properties compared to those of the prior art.
It is a further object of the present invention to provide a friction material having improved "shudder resistance", "hot spot" resistance, high heat resistance, high friction stability and durability, and strength.

  The present invention relates to a friction material having a first layer comprising a porous substrate comprising at least one type of friction modifying particles in the substrate, wherein the friction modifying material is of at least one type of nanoparticle size. Contains friction modifying particles.

  Nanoparticle-sized friction modifying particles are deposited as a porous or discontinuous layer on the upper surface, whereby the upper layer has substantially the same permeability as the first layer. Nanoparticle-sized friction modifying particles are deposited on the surface of the individual fibers and / or fillers that make up the substrate or second layer of friction material; or, if it is a nonwoven material, randomly on the surface of the friction material Deposit on the surface of the spaced part. The individual fibers and / or fillers that make up the friction material may have a layer of nanoparticle-sized friction modifying particles having a thickness of about 0 to about 250 μm on the surface of such individual fibers and / or fillers. it can. The nanoparticle-sized friction modifying particles have an average diameter size of about 10 nm to about 150 nm. In certain embodiments, the nanoparticle layer covers from about 0 to about 99 area percent of the individual fibers and / or fillers of the substrate, and in other embodiments, the nanoparticles have from about 3 to about 20 areas. % Coating. Further, in certain embodiments, the nanoparticles at least partially cover individual fibers and / or fillers of the substrate.

  In certain preferred embodiments, the friction modifying particles comprise silica nanoparticles. In certain other embodiments, the friction modifying particles can further comprise silica nanoparticles and at least one other nanoparticle sized friction modifying particle.

  In one aspect, the friction material comprises a first layer having a porous substrate and at least one type of resin material, and at least one type of nanoparticle size that at least partially covers the top surface of the porous substrate. A second layer having a friction modifying particle. The second layer has an average thickness ranging from about 0 to about 200 μm on the individual fibers and / or filler surfaces comprising the substrate, whereby the top layer is substantially the same as the first layer. Have the same or greater permeability. In certain embodiments, the layer of nanoparticle-sized friction modifying particles on the individual fibers and / or filler surfaces that comprise the porous substrate is thicker on the surface of such individual fibers and / or filler particles. About 75 to about 85 μm. In certain embodiments, the top layer has substantially the same or greater permeability in the radial direction and substantially the same or greater permeability in the vertical direction than the porous substrate.

  In accordance with the present invention, a layer of nanoparticles is deposited on and within the fibrous friction substrate. The substrate fibrous layer is partially coated with nanoparticles. The nanoparticles penetrate into the internal structure and adhere to the surface of the substrate fibers and / or filler components.

  While not wishing to be bound by theory, it is believed that the nanoparticles impart additional mechanical strength and increased friction properties to the friction material when adhered to the substrate fibers. Nanoparticles are present in the substrate due to their very small size and because of the relatively large surface area provided by the fiber / filler itself compared to the nanoparticles and Adhere to the surface of the filler. The fact that the nanoparticles are very small compared to the fibers / fillers in the substrate means that the nanoparticle-sized friction modifying material is a constituent of the substrate (ie, fibers and / or fillers, for example). It is possible to distribute substantially uniformly over the entire surface.

  One advantage of depositing such nanoparticles on the surface of the individual fibers and / or fillers that make up the substrate is that the friction performance is enhanced (eg, higher coefficient of friction, better mu- v gradient, and the like).

  In certain embodiments, the nanoparticles have a diameter size ranging from about 10 nm to 150 nm. Also, in certain embodiments, the nanoparticles form clusters of nanoparticles that accumulate in groups or clumps on the surface of the individual fibers and / or fillers that make up the substrate.

  According to another aspect of the present invention, the nanoparticle friction modifying particles form an open or substantially porous layer that is more permeable than the substrate layer. The higher permeability of the top layer of nanoparticle friction modifying particles still allows the friction material to retain the desired amount of fluid on the top surface of the friction material, while at the same time providing a friction material having the desired properties.

  In a particular embodiment, the present invention relates to a friction material having a porous or lofty open substrate. The friction material has a desired low density and a fiber structure that allows the resin material to penetrate into the friction material. The friction material has very good heat resistance and coefficient of friction properties that allow the friction material to respond satisfactorily under thermal and mechanical stresses.

  In another aspect, the invention relates to a “macroporous” fibrous substrate (eg, a woven substrate) having a surface partially coated with a nanoparticle sized friction modifying material. The large pores in the porous substrate allow the nanoparticle sized friction modifying material to settle into voids or gaps in the porous substrate. In the macroporous friction material of the present invention, the large pores allow contaminants in the fluid to easily pass through the friction material. As is well known to those skilled in the art, lubrication degrades over time and debris is generated. The friction material of the present invention maintains the friction behavior of the friction material constant throughout the useful life of the friction material.

  In one embodiment of the present invention, the average void volume of the substrate is from about 40 to about 80%. In certain embodiments, the substrate has an average pore / void / gap diameter of about 2 to about 10 μm and an average diameter of about 5 to about 7 μm.

Further, in certain embodiments, the friction modifying particles comprise silica nanoparticles, and in other embodiments, the nanoparticles can be combined with a mixture of other friction modifying particles.
The nanoparticles of friction modifying particles in the substrate give the resulting friction material an improved three-dimensional structure.

  The substrate has an average void volume of about 60 to about 85%. In certain embodiments, the porous substrate layer comprises about 70-85% by weight fibers and 10-30% by weight filler. In certain embodiments, the porous substrate can include about 80% fibers and about 20% filler.

  In another aspect, the present invention relates to a method for producing a friction material, wherein a porous substrate is saturated with a saturant. The saturant can include at least one resin material and at least one type of nanoparticle sized friction modifying particles, whereby a plurality of nanoparticle sized friction modifying particles can be separated into individual substrates comprising the substrate. A layer is formed on the surface of the fiber and / or filler. In certain embodiments, the upper layer is substantially more permeable than the first layer and cures the saturated substrate at a predetermined temperature for a predetermined time.

  In another aspect, the method includes producing a saturant material comprising at least one curable resin material and at least one type of nanoparticle-sized friction modifying particles, and a plurality of dispersed through the plurality of saturant materials. Producing a porous substrate having a gap, and producing a friction material by saturating the porous substrate with a saturant material, whereby the individual fiber surfaces comprising the substrate A plurality of nanoparticle sized friction modifying particles are at least partially deposited to distribute the resin material substantially uniformly throughout the substrate.

  To achieve the requirements discussed above, many friction materials were evaluated for friction and heat resistance properties under conditions similar to those occurring during use. A commercial friction material was investigated and found to be unsuitable for use in high energy applications.

In accordance with the present invention, the friction material provides a uniform dispersion of the curable resin throughout the porous substrate and a substantially non-uniform layer of nanoparticle-sized friction modifying material in the porous substrate. Have.
In one aspect, the substrate layer comprises a highly porous material, such as a long fiber woven material, and in another aspect, a highly porous nonwoven material. In certain embodiments, the porous substrate has a high fiber content within the range of about 75 to about 85%, based on the total weight of the substrate, and in certain embodiments, about 80% by weight. It is. The substrate has a filler content in the range of about 15 to about 25% by weight, based on the total weight of the substrate, and in certain embodiments is about 20% by weight. Less filler in the substrate significantly improves lateral permeability.

  In yet other embodiments, the nanoparticle sized friction modifying particles can also include other friction modifying particles such as metal oxides, nitrides, carbides, and mixtures thereof. Specific examples thereof include, for example, silica oxide, iron oxide, aluminum oxide, titanium oxide and the like; silica nitride, iron nitride, aluminum nitride, titanium nitride and the like; and silica carbide, iron carbide It is within the anticipated scope of the present invention to include aluminum carbide, titanium carbide and the like.

  A variety of substrates are useful in the friction material of the present invention, such as non-asbestos fibrous substrates including, for example, fabric materials, woven materials, and / or nonwoven materials. Suitable fibrous substrates include, for example, fibers and fillers. The fibers can be organic fibers, inorganic fibers and carbon fibers. The organic fibers can be aramid fibers such as fibrillated and / or non-fibrillated aramid fibers, acrylic fibers, polyester fibers, nylon fibers, polyamide fibers, cotton / cellulose fibers and the like. The filler can be, for example, silica, diatomaceous earth, graphite, alumina, cashew dust, and the like.

  In other embodiments, the substrate can include a fibrous woven material, a fibrous nonwoven material, and a paper material. In addition, examples of various types of fibrous substrates useful in the present invention are disclosed in the above referenced Borg Warner US patent, which is hereby fully incorporated by reference. However, it should be understood that other embodiments of the present invention may further include different substrates.

  In certain embodiments, the friction material includes a substrate having a plurality of voids or gaps therein. The size of the voids in the fibrous base material can range from 0.5 μm to about 20 μm.

  In certain embodiments, the substrate preferably has a void volume of about 50 to about 60%, so that the fibrous substrate is “dense” compared to a “porous” woven material. Is considered.

  In one aspect of the invention, the invention relates to a friction material having a novel, microstructured surface. A friction material having a microstructured surface has a higher coefficient of friction, more robust anti-skid properties, and extremely high heat resistance.

  In one aspect, the present invention relates to a friction material having a porous or bulky open substrate. The material has a low density and a fiber structure that allows the resin material to penetrate into the friction material. The friction material has very good heat resistance and coefficient of friction properties that allow the friction material to respond satisfactorily under thermal and mechanical stresses.

  In another embodiment, the “macroporous” fibrous material has a surface that is not partially coated with a friction modifying material. The large pores allow the nanoparticle sized friction modifying material to settle into voids or gaps in the substrate. In the macroporous friction material of the present invention, the large pores allow contaminants in the fluid to pass through easily. As lubrication degrades over time, debris forms. The friction material of the present invention maintains the friction behavior of the friction material constant.

  In certain embodiments, the friction material further includes a resin material that at least partially fills the voids in the fibrous base material. The resin material is substantially uniformly dispersed throughout the thickness of the substrate.

  In certain embodiments, the substrate comprises a fibrous substrate, wherein less fibrillated fibers and carbon fibers are used in the fibrous substrate to provide the desired pore structure to the friction material. . The fiber geometry not only provides improved heat resistance, but also provides delamination resistance and squeal or noise resistance. In certain embodiments, the presence of carbon fibers and carbon particles helps to improve the heat resistance of the fibrous base material, maintain a stable coefficient of friction, and improve squeal resistance. In certain embodiments, cotton fibers can be included in the fibrous base material to improve the clutch “break-in” characteristics of the friction material.

  In certain embodiments, the use of less fibrillated aramid fibers and carbon fibers in the fibrous base material improves the ability of the friction material to withstand high temperatures. Less fibrillated aramid fibers generally have few fibrils attached to the core fibers. By using less fibrillated aramid fibers, a friction material with a more porous structure is obtained; that is, there are larger pores than when using typical fibrillated aramid fibers. A porous structure is generally defined by pore size and liquid permeability.

  Also, in certain embodiments, it is desirable for the aramid fibers to have a length ranging from about 0.5 to about 10 mm and a Canadian Standard Freeness (CSF) greater than about 300. In certain embodiments, less fibrillated aramid fibers having a CSF of about 450 to about 550, preferably about 530 or more; in other specific embodiments, about 580 to 650 or more, preferably about 650 or more. It is also desirable to use it. In contrast, more fibrillated fibers, such as aramid pulp, have a freeness of about 285-290.

  “Canadian Standard Freeness” (T227 om-85) means that the degree of fibrillation of a fiber can be expressed as a measure of the freeness of the fiber. The CSF test is an experimental procedure that gives an arbitrary measure of the rate at which a suspension of 3 grams of fiber in 1 liter of water can be drained. Thus, less fibrillated aramid fibers have a higher freeness or greater drainage rate of fluid from the friction material than more fibrillated aramid fibers or pulp. A friction material comprising aramid fibers having a CSF ranging from about 430 to 650 (in certain embodiments, preferably about 580 to 640, or preferably about 620 to 640) provides excellent friction performance, and It has better material properties than conventional friction materials containing more fibrillated aramid fibers. The higher fiber length gives the friction material high strength, high porosity and good wear resistance in addition to high Canadian freeness. Less fibrillated aramid fibers (CSF about 530 to about 650) have particularly good long-term durability and a stable coefficient of friction.

  Various fillers are also useful in the primary layer of the fibrous base material of the present invention. In particular, silica fillers such as diatomaceous earth are useful. However, it is expected that other types of fillers will be suitable for use in the present invention and that the choice of filler will depend on the individual requirements of the friction material.

  In certain embodiments, cotton fibers are added to the fibrous base material of the present invention to give the friction material a higher coefficient of friction. In certain embodiments, about 10 to about 20%, and in certain embodiments about 10% cotton can also be added to the fibrous base material.

  One example of a formulation for the primary layer of the fibrous base material is about 15 to about 25% cotton, about 40 to about 50% aramid fiber, about 10 to about 20% carbon fiber, about 5 to about 15% carbon particles, about 5 to about 15% celite, and optionally about 1 to about 3% latex added.

  If the substrate has a higher mean pore diameter and fluid permeability, the friction material is due to a better flow of automatic transmission oil throughout the porous structure of the friction material, Probably operating at lower temperatures or generating less heat in the transmission. During operation of the transmission system, especially at high temperatures, the fluid tends to decompose over time and form “oil deposits”. These “oil deposits” reduce pore openings. Thus, if the friction material initially has larger pores, more open pores will remain throughout the useful life of the friction material.

The friction modifying particles in the fibrous base material give the resulting friction material an improved three-dimensional structure.
The friction modifying material layer retains the fluid lubricant in the substrate and increases the oil retaining capacity of the friction material. The friction material of the present invention thus allows an oil film to remain on the surface. This also gives good coefficient of friction properties and good slip durability properties.

  In certain embodiments, the average coverage area of the friction modifying particles forming the top layer is in the range of about 0 to about 50% of the surface area. In certain other embodiments, the average coverage area ranges from about 40 to about 50%.

  The amount of coating of nanoparticle-sized friction modifying particles on the surface of the fibrous base material is made sufficiently random so that the individual fibers of the substrate and / or the layer of nanoparticle-sized friction modifying particles on the filling surface are tertiary. Have the original structure. This three-dimensional structure is composed of individual fibers and / or filler surfaces of the substrate and individual particles of friction modifying material in voids or gaps between the individual fibers. In certain embodiments, the upper layer (of nanoparticle-sized friction modifying particles) is as porous or more porous as the lower layer (of the fibrous base material).

  In order to achieve uniformity of deposited nanoparticle-sized friction modifying particles in the substrate, the primary particle size of the friction modifying particles may range from about 10 to about 150 nm in diameter, preferably from about 10 to about 50 nm. Use size. In certain embodiments, the particles have an average nanoparticle diameter of about 15 nm to about 30 nm as the primary nanoparticle size.

  Various types of nanoparticle-sized friction modifying particles are useful in the friction material. In one embodiment, useful friction modifying particles include silica particles. Other embodiments can have resin powders such as phenolic resins, silicone resins, epoxy resins and mixtures thereof as examples of nanoparticle sized friction modifying particles. Still other embodiments include partially and / or fully carbonized nanoparticle-sized friction modifying particles carbon powder and / or particles and mixtures thereof; and mixtures of such nanoparticle-sized friction modifying particles. It is done. In certain embodiments, nano-sized silica particles such as diatomaceous earth, Celite®, Celatom®, and / or silicon dioxide are particularly useful. Nanoparticle-sized silica particles are inorganic materials that bind strongly to the substrate. Nanoparticle-sized silica particles give the friction material a high coefficient of friction. Nanoparticle-sized silica particles also provide a smooth friction surface to the substrate and a good “shift feel” and friction properties to the friction material, thereby minimizing any “shudder”.

  In certain embodiments, the friction material can be impregnated using various resin systems. In particular embodiments, at least one phenolic resin, at least one modified phenol-based resin, at least one silicone resin, at least one modified silicone resin, at least one epoxy resin, at least one type It is useful to use modified epoxy resins and / or combinations of the above. In certain other embodiments, it is useful to blend or mix the silicone resin with the phenolic resin in a compatible solvent.

  A variety of resins are useful in the present invention. In certain embodiments, the resin may comprise a phenolic resin or a phenol-based resin, preferably such that the saturant material comprises from about 45 to about 65 parts by weight per 100 parts by weight of friction material. After the resin mixture is applied to the substrate and the substrate is impregnated with the resin mixture, the impregnated substrate is heated to a desired temperature for a predetermined length of time to form a friction material. In certain embodiments, heating cures the phenolic resin present in the saturant at a temperature of about 300 ° F. When other resins such as silicone resins are present in the saturant, the silicone resin is cured at a temperature of about 400 ° F. by heating. Thereafter, the cured friction material is adhered to the desired substrate by suitable means.

  Various useful resins include phenolic resins and phenol-based resins. A variety of phenolic-based resins, including other modifying ingredients such as epoxy, butadiene, silicone, tung oil, benzene, cashew nut oil and the like in the resin blend are expected to be useful in connection with the present invention. Should be understandable. In phenol-modified resins, the phenolic resin is generally present at about 50% or more (excluding any solvent present) by weight of the resin blend. However, the mixture is about 5 to about 80% by weight in certain embodiments, based on the weight of the silicone-phenolic resin mixture (excluding solvents and other processing acids), and about It has been found that the friction material can be improved if it comprises a resin blend comprising from 15 to about 55 wt.%, And in certain embodiments from about 15 to about 25 wt.% Silicone resin.

  Examples of phenolic resins and phenol-silicone resins useful in the present invention are fully disclosed in the above referenced Borg Warner US patent, which is hereby fully incorporated by reference. Examples of silicone resins useful in the present invention include thermosetting silicone sealants and silicone rubbers. A variety of silicone resins are useful in connection with the present invention. One resin comprises in particular xylene and acetylacetone (2,4-pentanedione). This silicone resin has a boiling point of about 362 ° F. (183 ° C.), a vapor pressure of 21 mm Hg at 68 ° F., a vapor density (air = 1) 4.8, negligible water solubility, specific gravity of about 1.09, percent volatilization Having a flash point of about 149 ° F. (65 ° C.) using the Pensky-Martens method. It should be understood that other silicone resins can be utilized in connection with the present invention. Other useful resin blends include, for example: (by weight) about 55 to about 60% phenolic resin, about 20 to about 25% ethyl alcohol, about 10 to about 14% phenol, about 3 to about 4 A suitable phenolic resin may be mentioned that contains about 0.3% methyl alcohol, about 0.3 to about 0.8% formaldehyde, and about 10 to about 20% water. Another suitable phenol-based resin is: (by weight) about 50 to about 55% phenol / formaldehyde resin, about 0.5% formaldehyde, about 11% phenol, about 30 to about 35% isopropanol, And about 1 to about 5% water.

  Another useful resin comprises from about 5 to about 25% by weight, preferably from about 10 to about 15% by weight of the epoxy compound, with the remainder (excluding solvents and other processing aids) being a phenolic resin. It was found to be an epoxy modified phenolic resin. The epoxy-phenolic resin compound imparts higher heat resistance to the friction material than in the case of the phenolic resin alone in certain specific examples.

  In certain embodiments, the target pickup of the resin by the substrate is from about 25 to about 70% by weight of the total silicone-phenolic resin, in other embodiments from about 40 to about 65% by weight, in certain embodiments It is preferred that the resin mixture comprises the desired amount of resin and nanoparticle sized friction modifying particles, ranging from about 60 to at least 65 wt%. After saturating the substrate with the resin, the substrate is cured at a temperature ranging from 300 to 400 ° C. for a period of time (about 1/2 hour in certain embodiments) to cure the resin binder, Form a friction material. The final thickness of the friction material depends on the initial thickness of the substrate.

  In addition, other ingredients and processing aids that are known to be useful in both resin blend manufacture and substrate manufacture can be included and are within the expected scope of the present invention. Is predicted.

  In certain embodiments, the resin mixture can include both a silicone resin and a phenolic resin present in a solvent that is compatible with each other. These resins are mixed together (in a preferred embodiment) to form a uniform blend, which is then used to saturate the fibrous base material. In certain embodiments, the same effect does not occur when the substrate is impregnated with a phenolic resin and then a silicone resin is subsequently added, and vice versa. There is also a difference between a silicone-phenolic resin solution mixture and an emulsion of silicone resin powder and / or phenolic resin powder. If the silicone resin and phenolic resin are in solution, they will not cure at all. On the other hand, the powder particles of silicone resin and phenol resin are partially cured. Partial curing of the silicone resin and phenolic resin inhibits good saturation of the substrate.

  In a particular embodiment of the invention, the substrate is impregnated with a silicone resin blend in a solvent, where the solvent is such that the phenolic resin and the solvent are compatible. In one embodiment, isopropanol has been found to be a particularly suitable solvent. However, it should be understood that a variety of other suitable solvents such as ethanol, methyl ethyl ketone, butanol, isopropanol, toluene and the like can be utilized in the practice of the present invention. When silicone resin is blended with phenolic resin and then used to saturate the substrate, the resulting friction material is more elastic than the substrate impregnated with phenolic resin alone due to the presence of silicone resin. Becomes larger. When pressure is applied to the friction material of the present invention blended and impregnated with a silicone-phenolic resin, a more uniform pressure distribution is obtained, thereby reducing the likelihood of non-uniform lining wear. After mixing the silicone resin and the phenolic resin with the friction modifying particles, the mixture is used to impregnate the substrate.

  The friction material of the present invention includes nanoparticle-sized friction modifying particles randomly dispersed inside the base material, and has good shudder resistance, high resistance, high coefficient of friction, high durability, good wear resistance and improved Imparts break-in performance to the friction material.

  FIG. 1 a is a schematic diagram showing a prior art friction material 10 having a fibrous base material 12 and diatom friction modifying particles 14. FIGS. 1b, 1c and 1d are schematic diagrams showing a comparison of the sizes of fibers (FIG. 1b), conventional silica particles (FIG. 1c), and nanoparticles used in the present invention (FIG. 1d). FIG. 2 is a schematic diagram of a fiber having nanoparticles on the surface of the fiber.

  In certain embodiments, it has been discovered that when the friction modifying particles are very small in size, the desired optimal three-dimensional structure is achieved, thus optimizing heat dissipation and anti-shudder properties.

  In certain embodiments, the friction modifying material nanoparticles are believed to form clusters or aggregates of nanoparticles on the surfaces of the individual fibers and fillers that form the outer surface of the substrate layer. In certain embodiments, the clusters have an average diameter of less than about 30-100 nm.

  The nanoparticle sized friction modifying material used in the porous friction material of the present invention provides good anti-shudder properties to the friction material. In the embodiment shown, the high temperature synthetic fibers and the porosity of the substrate provide improved heat resistance.

  In addition, the porous friction material has relatively large pores that allow fluid contaminants to pass through easily. This absorption of such degradation products gives the friction material a more constant friction behavior.

The gradient of nanoparticle-sized friction modifying particles within the friction material of the present invention provides an improvement over conventional friction materials. The friction material has desirable coefficient of friction, heat resistance and durability characteristics.
Depositing nanoparticle-sized friction modifying particles inside the substrate produces a porous surface layer that does not significantly reduce the permeability of the substrate. The permeability of the substrate allows fluids or lubricants to flow through the substrate and not remain retained on the surface of the friction material.

  The present invention is useful as a high energy friction material for use with clutch plates, transmission bands, brake shoes, synchronizer rings, friction discs or system plates.

  The above description of the preferred embodiments and other embodiments of the present invention is intended to be illustrative and not limiting of the scope of the claims and their contents.

FIG. 1a is a schematic diagram showing a prior art friction material having a fibrous base material and friction modifying particles.

FIG. 1b is a schematic showing the relative size of the particles, with a typical fiber diameter of 10-15 micrometers.
FIG. 1c is a schematic showing the relative size of the particles, showing 10-20 micrometers as a typical average size of diatom particles.

FIG. 1d is a schematic showing the relative size of the particles, showing a nanoparticle size of 0.01 micrometers.
1 is a schematic representation of a fiber having nanoparticles on the surface of the fiber.

Claims (26)

  A first layer comprising a porous substrate and at least one type of resin material, and a second layer comprising at least one type of nanoparticle-sized friction modifying particles that at least partially coats the top surface of the porous substrate. In the friction material, the second layer has an average thickness of about 0 to 200 μm on the surface of the individual fibers and fillers constituting the base material, and the upper layer is substantially the same as the first layer. A friction material that has the same or greater permeability.   The friction material of claim 1, wherein the layer of the nanoparticle-sized friction modifying particles on the individual fibers and filler surfaces that comprise the porous substrate has a thickness of about 75 to about 85 μm.   The friction material of claim 1, wherein the upper layer has substantially the same or greater permeability in the radial direction and substantially the same or greater permeability in the vertical direction than the porous substrate.   The friction material of claim 1, wherein the nanoparticle-sized friction modifying particles have an average diameter size of about 10 nm to about 150 nm.   The friction material of claim 1, wherein the size of the friction modifying particles is from about 1 to about 20 nm.   The friction material of claim 1, wherein the porous substrate has an average void volume of about 65 to about 85%.   The friction material according to claim 1, wherein the nanoparticle-sized friction modifying particles include silica particles.   The friction material according to claim 7, wherein the nanoparticle-sized friction modifying particles include celite particles.   The friction material of claim 7, wherein the nanoparticle-sized friction modifying particles comprise diatomaceous earth.   The friction material according to claim 1, wherein the nanoparticle-sized friction modifying particles include a mixture of carbon particles and silica particles.   The friction material of claim 7, wherein the celite has an irregular shape.   9. The friction material of claim 8, wherein the celite particles have a size ranging from about 2 to about 20 nm.   The friction material according to claim 1, wherein the nanoparticle-sized friction modifying particles include a metal oxide.   The friction material according to claim 1, wherein the nanoparticle-sized friction modifying particles include nitride.   The friction material according to claim 1, wherein the nanoparticle-sized friction modifying particles include carbide.   The friction material of claim 1, wherein the substrate comprises a fibrous substrate.   The friction material of claim 1, wherein the substrate is a nonwoven fibrous material.   The friction material of claim 1, wherein the substrate is a woven fibrous material.   The fibrous base material includes about 15 to about 25% cotton, about 40 to about 50% aramid fibers, about 10 to about 20% carbon fibers, about 5 to about 15% carbon particles, and about 5 to about 5%. 18. The friction material of claim 17, comprising about 15% celite, and optionally about 1 to about 3% latex.   20. The friction material of claim 19, wherein the upper layer of friction material comprises silica nanoparticle-sized friction modifying particles deposited on the surfaces of the fibers of the nonwoven fibrous material and the filler material in the fibrous base material. .   The friction material of claim 17, wherein the fibrous base material has an average pore diameter of about 5 μm.   The friction material of claim 1, wherein the resin comprises at least one phenolic resin or at least one modified phenolic resin.   The resin comprises a mixture of at least one phenolic resin and at least one silicone resin, and the amount of silicone resin in the resin mixture is from about 5 to about 80% by weight, based on the weight of the resin mixture. The friction material of claim 1 over a range. A method of manufacturing a friction material,
Saturating the porous substrate with a saturant comprising at least one resin material and at least one type of nanoparticle-sized friction modifying particles, whereby the plurality of friction modifying particles are separate fibers comprising the substrate A layer is formed on the surface of the filler, the layer of nanoparticle-sized friction modifying particles has an average thickness of about 0 to 200 μm, and the upper layer has substantially more permeability than the first layer;
Curing the saturated substrate at a predetermined temperature for a predetermined time;
Including methods. A method of manufacturing a friction material,
Producing a saturant material comprising at least one curable resin material and at least one type of nanoparticle-sized friction modifying particles;
Producing a porous substrate having a plurality of gaps dispersed therethrough;
Saturating the porous substrate with a saturant material, thereby at least partially depositing a plurality of nanoparticle-sized friction modifying particles on individual fiber surfaces comprising the substrate; A method of distributing the resin material substantially uniformly throughout the substrate.   26. The method of claim 25, wherein the nanoparticle sized friction modifying particles form a porous top layer on a surface of at least one surface of the substrate.

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